There is no difference in meaning between the adverbs daily/hourly/weekly/monthly, &c, and the preposition phrases on a daily/hourly/weekly/monthly basis deployed as adverbials.
The PPs are superfluous and verbose, but they have virtually replaced the adverbs in most contexts. Present-Day English has become more and more uncomfortable with deploying the same word as both an adjective and an adverb, and the discomfort is exacerbated when the word has the -ly suffix, which today is 'productive' only in creating adverbs. There is consequently a strong tendency to restrict ambivalent -ly words to adjectival use and express the adverbial sense with a PP. This is true not only of these time expressions but also other -ly adjectives—friendly, for instance, is very rarely employed as an adverb today, that sense being expressed by as a friend or in a friendly manner.